Make NoThrow FunctionLike, make FunctionLike include references, fix

Make NoThrow FunctionLike, make FunctionLike include references, fix
prettyprint

__declspec(nothrow) should work on function pointers as well as function
references, so this changes it to FunctionLike.  Additionally,
FunctionLike needed to be modified to permit function references.

Finally, the TypePrinter didn't properly print the NoThrow exception
specifier, so make sure we get that right as well.

llvm-svn: 362435